Typically, static electricity may be generated during the process of manufacturing an LCD panel driven by a thin-film transistor (TFT), such as during chemical vapor deposition (CVD), sputtering, dry etching, or the steps that utilize electronic plasma. In addition, static electricity may be introduced from the external environment during packaging or delivery.
Since the use of insulation glass as the substrate of an LCD panel restricts the removal of static electricity, the static electricity generated by the manufacturing process accumulates in the LCD panel to cause high potential difference between the LCD panel and the TFT. When the accumulated static electricity is discharged, an instantaneous current with high voltage can affect the function of the TFT and can even cause permanent damage. Therefore, eliminating electrostatic discharge form the LCD panel is an important aspect for increasing the manufacturing yield during the manufacturing process.
In the past, applying a static eliminator and developing the process steps have been applied to eliminate static electricity. However, these methods cannot eliminate static electricity completely to resolve the problems aforementioned.
Currently, an electrostatic discharge protection device is provided which serves as a short-ring circuit set around the active displaying area of a LCD panel. The short-ring circuit can direct the static electricity accumulated in the LCD panel out to protect the electrical devices from being damaged.
However, electromagnetic interference (EMI) generated by the short-ring circuit can interfere with the signals of the LCD panel. It has been found that the lower the resistance of the short-ring circuit, the more effectively the short-ring circuit can disperse static electricity. However, in this condition, the short-ring circuit generates EMI more easily. So, the use of such a short-ring circuit is rather limited.